It is common practice to utilize conveyors for moving articles about a factory, warehouse or loading dock. Such conveyors generally include rollers, at least some of which are driven, to advance goods along respective conveyors. Prior conveyor systems have utilized air pressure to power actuators moving articles along conveyors. Some conveyor systems have optically sensed the position of articles from below conveyor rollers.
FIGS. 1-3 illustrate parts of a known conveyor system 10 of the type extensively used in factories, warehouses and the like to permit supporting and advancing of articles such as boxes thereon. The conveyor 10 includes power-driven article support elements such as rollers 12 which are disposed to define an elongate path, and the rollers are typically rotatably supported so as to extend transversely between a pair of elongate side rails, one such side rail 11 being illustrated in FIG. 1. The conveyor 10, when configured to function as an accumulating conveyor, typically has the rollers 12 defined into adjacent zones which can be independently driven from one another. For this purpose, the rollers 12 of each zone are typically independently driven from a main drive device such as a continuously driven line shaft 14 which extends lengthwise of the conveyor. The rollers 12 of the individual zones are then independently and selectively driven from the line shaft 14 through an intermediate drive transmitting device 17 which can be selectively actuated. This intermediate drive transmitting device, in the illustrated embodiment, includes an elongate twisted belt 16 which is engaged between the line shaft 14 and drive hubs associated with one or more of the rollers 12 defining the respective zone. The drive belt 16 in turn has an actuator 18 associated therewith for appropriately tensioning or de-tensioning the drive belt. The actuator 18 in the illustrated embodiment includes an extendable and contractible fluid pressure device such as an air cylinder, the latter causing appropriate extension or contraction of a wheel 19 which contacts the drive belt 16 and can be moved into or away from the drive belt to effectively tension or de-tension same. By tensioning the drive belt 16, the frictional contact between the drive belt and the drive rollers 12 and line shaft 14 is sufficiently increased to effect driving rotation of the rollers 12, whereas conversely when the belt is de-tensioned the drive belt slips relative to the line shaft so that the rollers of the respective zone are not driven.
The general arrangement of the conveyor as described above, when used as an accumulating and advancing conveyor, permits individual articles to be supported on and advanced from zone to zone without permitting the articles to contact or stack against one another. This advancing of the articles from zone to zone is facilitated by a conveyor control system 21 which includes a series of zone control modules 22, only one of which is shown in FIGS. 1 and 2, disposed serially along the conveyor for controlling the individual zones.
In the known control system 21 illustrated by FIGS. 1 and 2, the zone control module 22 includes an optical sensor 33 which is disposed so as to project a sensing path 34 transversely across the rollers of an adjacent downstream zone so as to sense the presence or absence of an article in the zone which is located downstream from the zone being controlled by the respective control module 22. When the sensor 33 senses the absence of an article or box in the adjacent downstream zone, it transmits a signal to the controller 22 which in turn supplies pressure fluid to the air actuating device 18 associated with the adjacent upstream zone to activate the rollers 12 so that an article in the upstream zone is advanced into the adjacent downstream zone. Due to the presence of such control modules 22 being located in series and controlling the respective zones, articles can be sequentially advanced from zone to zone.
The control module 22 of the prior art, as shown by FIGS. 1 and 2, include an electrical unit 23 which plugs into an electrical solenoid unit 24, and the latter is fixedly secured to and operates a shiftable valve which is positioned interiorly of a manifold/valve unit 25. A cable 35 electrically connects the optical sensor to the electrical unit. The electrical control units 23 of serially adjacent modules 22 are in turn electrically interconnected by electrical conductors 37 which have plugs 36 at opposite ends for joining to connector parts 38 provided on opposite ends of the units 23 so as to electrically connect the adjacent control modules.
In similar fashion the valve/manifold unit 25 has a through flow passage 26 which terminates at connector hubs 27, and the adjacent modules 22 are joined together in fluid communication by fluid supply lines 28 connected to the hubs 27. The serially-connected fluid supply lines at a remote end are joined to an appropriate source of pressurized fluid, typically air. The unit 25 has a load port 29 which connects to a line 31 which in turn connects to the actuator device 18.
The control module, as illustrated by FIGS. 1 and 2, is typically fixedly secured to an inner surface of the side rails 11, such as by screws 32 extending therethrough and being secured directly into the housing of the valve/manifold unit 25.
With the arrangement illustrated by FIGS. 1 and 2, when the sensor 33 senses the absence of an article in the adjacent downstream zone, then a signal is transmitted to the electrical unit 23 which in turn energizes the shiftable solenoid associated with the solenoid unit 24, and this in turn activates the valve disposed interiorly of the valve/manifold unit 25. The activation of the valve permits pressurized fluid (i.e. air) from the supply line to pass through the valve to the fluid actuator 18 so that the belt associated with the upstream zone is tensioned to effect driving of the rollers 12 of the upstream zone, thereby permitting any article in the upstream zone to be advanced forwardly along the conveyor for movement into the adjacent downstream zone.
While the system described above relative to FIGS. 1-3 has generally operated in a satisfactory manner, nevertheless the construction thereof has possessed disadvantages. The construction of the module and the interrelationship between the units and the mounting thereof on the frame rail of the conveyor have made it difficult to service and maintain the arrangement. For example, if the valve/manifold unit requires repair or replacement, then the entire module must be removed to permit such repair, and then remounted on the side rail. Further, access to the solenoid unit is also difficult because of the overall constructional and positional restraints on the system, and thus any replacement or servicing thereof substantially requires removal of the entire module.
With the conveyor control arrangement of FIGS. 1-3, it is occasionally necessary or desirable to simultaneously activate a series of zones so as to permit simultaneous advancing of all objects or articles therein, this being referred to as "slug" advancing movement. To permit the simultaneous movement of a "slug" or series of articles, the control system of FIGS. 1 and 2 has the discharge port associated with each valve/manifold unit 25 connected to a discharge line. The discharge lines of the series of modules in turn connect to and discharge through a control valve which under normal conditions is maintained open to permit the normal discharge of air. This control valve is also connected to a slug line which in turn connects to a source of pressurized air. When slug movement is desired, the control valve is activated so that the discharge lines are closed off from the atmosphere, but instead are connected to the slug pressure line. The pressurized air in the slug pressure line is thus fed through the discharge lines to the discharge ports of the valve/manifold units, and is then fed through the valves to the pressure actuators 18 associated with the driving devices 17 associated with the series of zones, thereby permitting simultaneous driving of the rollers 12 in all of the zones defining the slug series. This slug movement is terminated by returning the control valve to the position wherein the slug pressure line is closed off and the discharge line are again vented. This known slug arrangement, however, significantly complicates the overall construction and specifically the pneumatic piping of the system.
Another prior art conveyor control device includes an optical sensor mounted below the rollers and angled upwardly to sense the presence or absence of articles through a gap between rollers. The optical sensor automatically closes a solenoid valve, turning off a section of the conveyor to avoid a collision when articles moving down the conveyor approach another article. The manner of mounting the device and the optical sensor therefore makes it difficult to accurately detect the presence of all articles on the conveyor.
Thus, it is an object of the invention to provide a conveyor control system which overcomes and/or improves on the disadvantages associated with the above prior art systems.
More specifically, this invention relates to a conveyor control system with simplified installation of the required wiring and plumbing, which system includes a control module having easy access and removal of the valve control unit without disturbing the manifold unit, and which can be used with a slug module to provide a simplified slug mode of operation.